The present invention relates in general to the packaging art, and is more particularly concerned with improvements in the sealing and cutoff means in forms, fill and seal machines wherein packages are formed from zippered foil or film material.
Numerous and varied sealing and cutoff mechanisms for form fill and seal machines are known. By way of example, U.S. Pat. Nos. 4,727,709 and 4,745,731 are referred to and which disclose forms of sealing and cutoff mechanisms wherein separate sealing bars and separate cutoff means are provided. The disclosures of these patents are incorporated herein to any extent necessary for full understanding of the present invention in relation to details not disclosed herein because conventional.
One of the problems that has been prevalent in prior apparatus has been the difficulty in attainment of leak-proof securement of the extruded plastic zipper in the packages produced by the machines. An expedient that has been used heretofore is ultrasonic pre-welding of the zipper in order to avoid leakage at the opposite ends of the zipper in the packages.
Another problem has been the general complexity of the cut-off and sealing mechanisms, especially in form, fill and seal machines which use zippered foil or film.